This invention relates to a method of deburring and polishing punched holes in mass produced parts of steel and other formable metals. The method is particularly well adapted for use in the manufacture of needles for sewing machines.
Several deburring and polishing processes have been used in the past. Chemical or electrolytic deburring and polishing are quite common. In the manufacture of sewing machine needles it is very common to thread the punched eye of the needle on a cotton thread to which emery paste has been added and then the emery-filled thread is placed in a machine specially built for the polishing operation. Deburring can also be accomplished by means of steel brushing.
An example of a method of producing sewing machine needle eyes by means of die-pressing operations is disclosed in the U.S. Pat. No. 3,333,623 issued Aug. 1, 1967. In this patented method the web that remains in the eye after all the die-pressing is completed must be removed by a punch-pin tool. This punch-pin operation does not polish the wall defining the eye. Consequently a separate eye polishing step is required satisfactorily to finish the eye.
While the above mentioned procedures are effective a careful control must be exercised to obtain the required tolerance in the polished eye or hole. Also these various methods require preparation work and subsequent cleaning and, thus, increase the cost of manufacturing.